Studies on membrane biogenesis are mainly concerned with the sites of synthesis and assembly of phospholipids and of enzymatic marker proteins. The approach utilizes combined biochemical, cytochemical and electron microscopic techniques and the major studies involve secreting cells of the ducklings' salt gland stressed by salt injestion. Other systems evincing rapid biogenesis of membranes include rapidly dividing tumor cells in culture and the development of thylakoid membranes of chloroplasts of Chlamydomonas (Y-1) exposed to light. Related studies involve NaKATPase (development of an immunocytochemical method and the use of ouabain derivatives to localize the activity), as well as enzymes involved in phospholipid synthesis, phosphatidic acid phosphatase and CDP amine and other diglyceride transferases. Some of these phospholipid methods are applied to studies concerning the biogenesis of pulmonary surfactant and in other studies involving the synthesis and packaging of glycolipids and glycoproteins.